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3.
Sleep in Christian & Jewish Philosophy
• According to the Bible, sleep is influenced by physical,
psychological and spiritual factors.
– Sleep is a gift from God
– Hard labor can induce the deepest form of sleep.
– Worry about material possessions results in sleeplessness.
• According to Jewish (Talmud) philosophy sleep is 1/60 of
death.
– Sleep is physical separation of the soul from the body.
– Soul comes back after sleep. It does not return after death.
– Refraining from sleep is a sin because sleep is enforced by
nature.
– God reaches out to us through dreams; bringing guidance,
nourishing our spirits, healing and refreshing us.

5.
Sleep investigations
• Modern sleep research is multidisciplinary.
• EEG has been the backbone of sleep research
and sleep medicine since 1930s.
• Analysis of sleep should ensure that it is:
– Compatible with existing scientific evidence.
– Based on biological principles.
– Applicable to clinical disorders.
– Easily used by sleep clinicians, sleep
scientists and technologists.

7.
Major issues in sleep analysis
• Our understanding of sleep and its neural mechanism is
grossly inadequate.
• Modern sleep classification is based on the age old belief
that sleep consists of REM sleep and Non-REM sleep.
• Classification of sleep into REM and Non-REM started with
the assumption that REM sleep is sleep with dream, and
Non-REM is dreamless sleep.
• Use of computer has helped in fast analysis of large data.
• But computer analysis has not been able to take care all
aspects of available information.
• There are major differences between manual (visual)
scoring, and computer scoring.

13.
Electroencephalography
• Modern sleep research began with electrophysiological
monitoring of sleep.
• The first person to record electric currents of the brain
was Richard Caton in1875.
• Hans Berger (1929) is generally credited with the
discovery of the EEG. He showed that the EEG differs
between sleep and waking.
• Aserinsky and Kleitman (1953) showed that sleep could
be further differentiated into two distinct states, ie REM
sleep and Non-REM sleep.
• EEG recorded from frontal, central and occipital regions
using 6 electrodes in10-20 system.

16.
Importance of power spectral
analysis of EEG
• Scoring more than 1400 pages of record is very time
consuming.
• Visual inspection & analysis of EEG bands, frequently do
not indicate the depth of sleep, and do not help to quantify
sleep.
• Therefore, automated scoring is essential.
• When a computer makes a hypnogram, it uses a lot of
parameters, such as alpha rhythm, sleep spindles, sleep
delta waves, rapid eye movements or tonic chin EMG
levels.
• The depth of sleep is reflected by EEG slow waves
produced during NREM sleep and tells us something about
its recuperative value.
• In all mammalian species delta waves increase as a
function of prior waking duration.

23.
Gamma oscillations
• Amplitude of gamma (35–45) oscillations is markedly
diminished in NREM sleep compared to wakefulness and
REM sleep.
(Llinas and Ribary, 1993)
Magnetoencephalography
(MEG) mapping of magnetic
fields produced by electrical
currents in the brain. MEG is
recorded using arrays of
SQUIDs (superconducting
quantum interference devices).

24.
EOG (Electroocculogram):
• EOG of REM sleep is characterised by bursts of Rapid Eye
Movements (REM).
• EOG - Awake or Stage N1 - regular, sinusoidal, initial deflection
>500msec
• EOG - Stage N3- not typically seen.
• EOG - REM sleep- irregular, sharp, initial deflection ≤ 500msec.
• Correlated with REM, there are PGO waves (best recorded with
depth electrodes in animals).
One electrode is placed above
and to the outside of the right
eye, and another placed below
and to the outside of the left eye.

25.
EMG (Electromyogram)
• Muscles are progressively relaxed during deeper NREM sleep.
• Maximum loss of muscle tone during REM sleep.
• Muscle relaxation is produced by progressive hyperpolarisation
of lower motor neurons.
• During REM sleep limb muscles show sudden twitches in
between.
Three leads are placed on the chin (one in the front
and center and the other two underneath and on the
jawbone).
Two leads are placed on the inside of each calf
muscle 2-4cm apart.

28.
EKG/ECG (Electrocardiogram)
• Two electrodes are placed on the
upper chest near the right and
left arms.
• These record the heart rate and
rhythm and serve to alert the
technician to a possible
emergency situation.
• They also demonstrate whether
apneic desaturation leads to
arrhythmias or not.

30.
Spectral analysis of HRV
• Power spectra of R-R intervals in sleep states
(Vanoli,1995; Otzenberger, 1998).
• Ratio of the low-to-high frequency spectra is used as
an index of parasympathetic-sympathetic balance.

38.
Human fMRI during sleep
• Though fMRI provides real-time imaging of neuronal
activity, this technique in sleep research has suffered
due to high noise levels in the scanner.
(Kaufmann et al, 2006).

39.
Sleep assessment: future-1
• Many physiological changes do occur during
sleep.
• Though we know the functions of some
physiological changes, there are many that we
still do not know.
• Present polysomnographic assessment is helpful
in clinical situations and in healthy subjects.
• But we are still far from adequate assessment of
sleep.
• Electrophysiologically and behaviorally defined
sleep do not explain all the aspects of sleep.
• Incorporation of more physiological parameters
will help in better analysis of sleep.

40.
Sleep assessment: future -2
• The present analysis of sleep does not provide
any quantification of dreams.
• It is essential to develop a technique to record
and quantify dream phase of sleep.
• There may be some basis in the ancient wisdom
of putting emphasis on dreams.
• Better quantitative and qualitative analysis of
sleep is essential for understanding its role in
health and survival.
• It also is essential for better clinical diagnosis.
• It is essential to continue with the manual scoring
and checking till a better system is evolved.